JPH07175485A - Structure of sound shielding wall - Google Patents

Abstract

PURPOSE:To reduce the size of a sound shielding structure by exhibiting a sound shielding function while assuring air permeability. CONSTITUTION:This structure has vibration systems having at least two sheets of sound shielding plates 23, 25 facing each other apart a spacing and apertures 27a, 27b, 29a, 29b disposed to face each other through these sound shielding plates 23, 25 and consists of the air mass (m) of these apertures 27a, 27b, 29a, 29b and air springs 37a, 37b of the air layer between the sound shielding plates 23 and 25. The structure is provided with plural kinds of vibrating systems 33a, 33b varying in resonance frequencies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound insulation wall structure capable of exhibiting a sound insulation effect while maintaining air permeability.

[0002]

2. Description of the Related Art Conventionally, as an automobile to which a sound insulation wall structure is applied, there is one shown in FIGS. 15 and 16, for example. This automobile 1 has an under cover 5 attached to the lower portion of an engine room 3. The under cover 5 has a function of improving the aerodynamic characteristics of the lower portion of the automobile 1 and a function of protecting the components in the engine room 3 from pebbles and the like that are flipped up, and suppressing noise emitted from the engine room 3 to the outside of the vehicle. It has a function as a sound insulation wall. The effect of the undercover 5 as a sound insulation wall increases as the area increases. However, as the area of the under cover 5 is increased, the lower portion of the engine room 3 is sealed, and the air temperature in the engine room 3 rises. As a result, the temperature inside the engine room 3 becomes high, which may lead to an unfavorable state in terms of component durability. As described above, when installing the undercover 5 in the engine room 3, not only the noise suppression aspect but also the thermal aspect must be considered.

Therefore, there is a conventional one as shown in FIGS. 17 and 18 (see Japanese Patent Application Laid-Open No. 60-85043). That is, in this conventional example, the noise control member 7 is provided in the lower opening of the engine room 3 of the automobile 1 instead of the under cover. This noise control member 7 has a large number of hollow pipe lines 9. The hollow conduits 9 are arranged such that the conduit length becomes shorter from the central portion of the noise control member 7 to the peripheral portion thereof. With this structure, the phase of the sound radiated from the engine room 3 is shifted according to the difference in the length of the hollow pipes 9, and the sound is shielded by canceling each other. Therefore, in this conventional example, the noise can be shielded by the noise control member 7, and the heat in the engine room 3 can be released to the outside through the hollow pipe line 9 to lower the air temperature in the engine room 3. be able to.

[0004]

However, the size of the undercover is a problem when it is actually mounted on an automobile as an undercover or the like. In other words, in the case of the undercover 5 in the engine room 3, the minimum ground clearance must be taken into consideration because it is installed between the engine room components such as the engine and the road surface. Actually, the space where the under cover 5 can be installed is the space from the minimum ground clearance to the parts in the engine room. Therefore, the undercover is restricted by its size, especially its thickness.

As described above, the noise control member 7 of FIG. 18 has a structure in which the transmitted sounds cancel each other out due to the phase difference due to the difference in the path length of the sound, that is, the difference in the length of the hollow conduit 9, so that the sound is blocked. In order to obtain the sound insulation effect, the path length difference of the hollow pipe 9 must be made by half wavelength. For this reason, in order to provide a sound insulation effect to a frequency having a relatively long wavelength, which is a problem with the noise outside the vehicle, the path length difference of the hollow pipe line 9 must be made long. There is a problem that it becomes too thick to be used as an undercover.

The present applicant has already applied for a sound insulation wall structure for solving such a problem as shown in FIGS. 19 and 20 (Japanese Patent Application No. 57196/1993). That is, the sound insulation wall 10 is provided with at least two sound insulation plates 11 and 13 that are opposed to each other with a space therebetween, and the sound insulation plates 11 and 13 are provided with openings 11a and 13a that are opposed to each other. The air 15 existing in the openings 11a and 13a is an air mass m, and the air existing between the sound insulation plates 11 and 13 is an air spring 17 having a spring constant k.
A vibration system with two degrees of freedom is constituted by 7 and 7.

In such a two-degree-of-freedom vibration system, the vibration transmissivity is less than 1 at the resonance frequency or higher and enters the vibration isolation region. By utilizing such a mechanism, the sound insulation effect can be obtained by the sound insulation wall structure as shown in FIG. Therefore, it is not necessary to take a long path length difference as in FIGS. 17 and 18, and it is possible to reduce the distance between the sound insulating plates 11 and 13 and obtain the thin sound insulating wall 10 advantageous as an undercover.

On the other hand, the resonance frequency of the vibration system including the air mass m and the air spring 17 must be made smaller in order to obtain the sound insulation effect from the low frequency by the above structure. For this purpose, the distance between the sound insulating plates 11 and 13 is increased to reduce the spring constant k of the air spring 17, or the thickness of the sound insulating plate 11 is increased to increase the openings 11a and 13.
It was necessary to increase the mass m of the air 15 existing in a and further reduce the aperture ratio. However, if the distance between the sound insulation plates 11 and 13 is increased or the thickness is increased, the sound insulation wall 1
There is a problem in that the thinness of 0 is limited, and the air permeability is sacrificed when the aperture ratio is reduced.

Therefore, an object of the present invention is to provide a sound insulating wall structure which is air permeable and which can be made thinner and smaller.

[0010]

In order to solve the above-mentioned problems, the invention of claim 1 is provided with at least two sound insulating plates facing each other with a gap, and penetrating each of the sound insulating plates.
A vibrating system having openings facing each other, the air mass of the openings and an air spring of an air layer between the sound insulation plates, and the vibrating system having a plurality of different resonance frequencies. Characterize.

A second aspect of the present invention is the sound insulation wall structure according to the first aspect, wherein the plurality of types of vibration systems are provided between the sound insulation plates and partition a predetermined vibration system from other vibration systems. It is characterized by being formed of a wall.

The invention according to claim 3 is claim 1 or claim 2.
The sound insulation structure according to claim 1, wherein the plurality of types of resonance frequencies are set such that a main frequency of sound intended for sound insulation exists in a frequency band between the minimum and the maximum of the resonance frequencies. Is characterized by.

According to a fourth aspect of the present invention, there are provided at least two sound insulating plates facing each other with a space therebetween, and a plurality of openings provided so as to penetrate through each of the sound insulating plates and facing each other.
Of each of the plurality of openings, a vibration system including an air mass of a predetermined opening and an air spring of an air layer between the sound insulation plates is provided,
It is characterized in that openings other than the openings constituting the vibration system are communicated between the sound insulating plates facing each other by a tubular portion having an inner surface of substantially the same cross section as the opening.

A fifth aspect of the present invention is the sound insulating structure according to the fourth aspect, wherein the resonance frequency of a vibration system formed by the air mass of the opening and the air spring of the air layer between the sound insulating plates is used for sound insulation. It is characterized in that it is lower than the main frequency of the sound to be.

A sixth aspect of the present invention is the sound insulation wall structure according to the fourth aspect, wherein a plurality of types of the vibration system are provided so that resonance frequencies are different, and the resonance frequency is a main frequency of sound intended for sound insulation. Is set to be a frequency band between the minimum resonance frequency and the next minimum resonance frequency.

The invention of claim 7 is the sound insulation wall structure according to any one of claims 1 to 6, wherein the sound insulation plate is an undercover of an engine room of an automobile.

The invention of claim 8 is the sound insulation wall structure according to any one of claims 1 to 7, wherein the opening is provided with an extension portion projecting to the opposite side of the sound insulation plate.

The invention of claim 9 is the sound insulation wall structure according to any one of claims 1 to 8, wherein a sound absorbing material is provided between the sound insulation plates.

[0019]

According to the invention of claim 1 of the above-mentioned means, in the sound insulating plates having the openings and facing each other, the air in the openings serves as an air mass and the air layer between the sound insulating plates acts as an air spring. Therefore, a pair of air masses are connected via an air spring to form a two-degree-of-freedom vibration system. Here, when sound enters from one of the vibration systems, the incident wave is transmitted to the other through the vibration system. At this time, when the frequency of the incident wave exceeds the resonance frequency of the vibration system, the phase of the transmitted wave is inverted by 180 degrees. Therefore, when a plurality of types having different resonance frequencies are provided as the vibration system, the phase of the transmitted wave from each different vibration system is 18
It is possible to create frequencies that are offset by 0 degrees, which causes the transmitted waves to cancel each other. Further, it is possible to ventilate the sound insulating plate from one side to the other side through the opening.

According to the invention of claim 2, in addition to the operation of the invention of claim 1, a vibration system having different resonance frequencies can be formed by partition walls provided between the sound insulating plates.

According to the invention of claim 3, in addition to the operation of the invention of claim 1 or 2, when the frequency of the sound for sound insulation exceeds the minimum resonance frequency, the phase of the transmitted wave is inverted by 180 degrees. Therefore, the phases of the transmitted waves in the vibration system having the maximum and minimum resonance frequencies are shifted by 180 degrees, and the sounds can be canceled by the transmitted waves.

According to the fourth aspect of the present invention, the portion in which the opening is communicated with the cylindrical portion having the inner surface of substantially the same cross section constitutes a one-degree-of-freedom vibration system having no resonance point. Therefore, there is no phase shift between the transmitted wave that has passed through this portion and the incident wave. On the other hand, the transmitted waves that have passed through the vibration system composed of the air mass and the air spring are out of phase. Therefore, both transmitted waves can cancel each other.

According to the invention of claim 5, in addition to the operation of the invention of claim 4, since the resonance frequency of the vibration system composed of the air mass and the air spring is smaller than the frequency of the sound for sound insulation,
The incident wave can be transmitted with a phase shift of 180 degrees.

According to the invention of claim 6, in addition to the operation of the invention of claim 4, the frequency of the sound for the purpose of sound insulation is a frequency band between the minimum resonance frequency of the vibration system and the next smallest resonance frequency. Therefore, the transmitted waves that have passed the minimum resonance frequency are 180 degrees out of phase with each other, and can cancel each other with the transmitted waves that have passed the other portions.

According to the invention of claim 7, the sound insulation wall structure can be used as an undercover of an engine room of an automobile.

According to the invention of claim 8, since the extension is provided in the opening so as to project to the opposite side of the sound insulating plate, the air mass of the opening can be increased and the resonance frequency can be reduced.

According to the ninth aspect of the invention, sound can be absorbed by the sound absorbing material provided between the sound insulating plates.

[0028]

Embodiments of the present invention will be described below.

FIG. 1A is a schematic sectional view of a sound insulation wall 21 to which the sound insulation wall structure according to the first embodiment of the present invention is applied. The sound insulation wall 21 has two sound insulation plates 23 and 25 facing each other with a space. The sound insulation plates 23, 25
Need only have at least two, and the number can be further increased.

A plurality of openings 27a, 27b, 29a, 29b facing each other are provided through the sound insulation plates 23, 25, respectively. The sound insulation plate 2
A partition wall 31 is provided between 3 and 25. Therefore, a plurality of vibration systems 33a and 33b are provided, and the partition wall 3
1 has a configuration in which a predetermined vibration system 33a is partitioned from another vibration system 33b.

The vibration system 33a has openings 27a and 27b.
Sound insulation plate 2 surrounded by the mass m of the air 35 and the partition wall 31
It is composed of an air spring 37a composed of an air layer between 3, 25. The other vibration system 33b similarly has openings 29a,
It is composed of an air mass m of the air 35 of 29b and an air spring 37b. The difference of the air layer volume between compartmented noise insulating plates 23 and 25 with the spring constant k ₁ and the partition wall 31 and the spring constant k ₂ of the air spring 37b of the pneumatic spring 37a, k ₁ <k
There is a relationship of ₂ . Therefore, a plurality of types of vibration systems 33a and 33b having different resonance frequencies are provided. The plural kinds of resonance frequencies of the vibration systems 33a and 33b are set so that the frequency of the sound for sound insulation exists in the frequency band between the minimum and the maximum of the resonance frequency.

The setting of the plural kinds of resonance frequencies will be described in comparison with the vibration system shown in the prior application of FIG. 1 (b).

In FIG. 1B, partition walls 31 between the sound insulating plates 11 and 13 are evenly provided for the openings 11a and 13b. When the partition plates 31 are evenly provided in this way, it is equivalent to the sound insulation wall 10 described with reference to FIGS.
That is, the sound insulation wall 10 described with reference to FIGS. 19 and 20 does not have a partition wall, but the spring constants of the air springs 17 with respect to the air mass m of each air 15 are all equal, and as shown in FIG. It is equivalent to a case in which all the air layer volumes are divided. Therefore, as shown in FIG.
When the size of the air layer divided by 1 is different, an increase in the volume of the air layer corresponds to a decrease in the spring constant of the air spring, and the resonance frequency of the predetermined vibration system 33a is different from that of other vibrations. It becomes smaller than the resonance frequency of the system 33b.

When sound enters from one of the sound insulation walls 21, the incident wave is transmitted to the other through the vibration systems 33a and 33b. At this time, when the frequency of the incident wave exceeds the resonance frequency of the vibration system, the phase of the transmitted wave is inverted by 180 degrees. Therefore, in this embodiment in which the vibration systems 33a and 33b having large and small resonance frequencies are provided, the phase of the transmitted wave is shifted by 180 degrees when the resonance frequency of the smaller vibration system 33a is exceeded. Further, since the resonance system is formed so that the frequency of the sound intended for sound insulation exists in the frequency band between the large and small resonance frequencies, the transmitted wave of the vibration system 33b having a large resonance frequency has no phase shift. . Therefore, the noises transmitted through both the vibration systems 33a and 33b cancel each other out, and a sound insulation effect can be provided in this frequency band. Further, regarding ventilation, one of the openings 27a, 27b, 2 from the sound insulation wall 21
Air can pass through 9a and 29b to provide sufficient air permeability.

In addition, in this embodiment, FIG.
As is clear from comparison with (b), the device can be downsized. That is, FIG. 1B shows the partition wall 3
1, but the partition wall 31 has the entire opening 11a,
It is equidistant from 11b, which is equivalent to the case where no partition wall exists between the sound insulation plates 11 and 13 in FIGS. In contrast to FIG. 1 (b), in the case of FIG. 1 (a), the partition wall 31 is moved closer to the openings 29a and 29b, so that the partition wall 31 has an opening when compared with FIG. 1 (b). It is in a state of moving away from the portions 27a and 27b. Therefore, the air mass of the air layer between the sound insulating plates 23 and 25 in the openings 27a and 27b becomes relatively large, and the spring constant of the air spring 37a can be reduced.
Therefore, the resonance frequency of the vibration system 33a becomes small. This means that when the same size as that of FIG. 1 (b) is considered, the sound insulation effect is obtained from a lower frequency, and conversely, when the sound insulation effect is provided from the same frequency, Since it is not necessary to increase the thickness to secure the volume of the air chamber and reduce the spring constant k, the one shown in FIG. 1 (a) can be made smaller than that shown in FIG. 1 (b). It becomes.

Next, another embodiment will be described. In the following embodiments, the same components as those in the above embodiment will be denoted by the same reference numerals and will not be described.

2 and 3 show a second embodiment.

In this embodiment, a sound insulation wall structure is applied to the under cover 5 of the automobile 1. That is, the under cover 5 is provided in the lower part of the engine room 3, and the sound insulation wall 39 is integrally provided on the rear side thereof. The concrete construction of the sound insulation wall 39 of the second embodiment is as shown in FIGS.

In this embodiment, each of the plurality of openings 27a,
Predetermined openings 27a, 2 of 27b, 29a, 29b
The air mass m of the air 35 of 7b and the air spring 37 having the spring constant k of the air layer between the sound insulating plates 23 and 25 constitute a vibration system 33a having two degrees of freedom. Further, the openings 29a and 29b other than the openings 27a and 27b constituting the vibration system 33a are communicated with each other by the tubular portion 41. The tubular portion 41 is provided between the sound insulating plates 23 and 25 that face each other, and has an inner surface having substantially the same cross section as the openings 29a and 29b. Therefore, the openings 29a, 2
The vibration system configured by 9b and the cylindrical portion 41 has an opening 29
The entire air 43 from a, 29b to the tubular portion 41 acts as an air mass M, and constitutes a vibration system 45 with one degree of freedom. This one-degree-of-freedom vibration system 45 does not have a resonance point, and the incident wave and the transmitted wave always have the same phase. On the other hand, the vibration system 33a having two degrees of freedom has a resonance frequency represented by the following equation.

[0040]

[Equation 1] The resonance frequency of the two-degree-of-freedom vibration system 33 is set to be lower than the frequency of sound intended for sound insulation. That is, in the case of engine noise of automobile 1, its frequency band is 1
.About.2.5 kHz, and the resonance frequency shown by the equation (1) is set to less than 1 kHz.

Therefore, in this embodiment, the engine room 3
When noise that leaks from the outside into the undercover 5 is incident on the undercover 5, the incident wave passes through as a transmitted wave having the same phase in the vibration system 45 with one degree of freedom, and the vibration system 3 with two degrees of freedom is used.
In 3a, the phase is shifted by 180 degrees and the light is transmitted by exceeding the resonance frequency represented by the equation (1). Therefore, the transmitted waves that have passed through the vibration system 45 and the vibration system 33a have mutually opposite phases and cancel each other, so that a sound insulation effect can be obtained. Especially in the case of engine noise of the automobile 1,
Since the frequency band is 1 to 2.5 kHz, the sound insulation wall 39 of the under cover 5 can have a reliable sound insulation effect against engine noise by setting the resonance frequency of the above formula (1) to less than 1 kHz. Of.

FIG. 6 is a calculation result confirming the effect of the sound insulation wall 39. In FIG. 6, β ₁ indicates the ratio of the number of openings 29a, 29b connected by the tubular portion 41 to the total number of openings 27a, 27b, 29a, 29b on the sound insulation wall 39. Then, the transmission loss of the sound insulation wall 39 was obtained by changing the ratio from 0 to 1. According to this, β
It was confirmed that when ₁ = 0.25, β ₁ = 0.5, β ₁ = 0.75, etc., the transmission loss was large and a sound insulation effect was obtained.

Further, in comparison with FIG. 1A, the tubular portion 41 has
Further, since the openings 29a and 29b are close to each other, it is possible to further reduce the size.

Further, in the second embodiment as well, the openings 27a,
Air permeability can be secured due to 29a, 27b, 29b, and hot air in the engine room 3 can be easily released to the outside.

Therefore, the under cover 5 of the automobile 1 is breathable and the engine room 3 from the minimum ground clearance.
It can be installed in a narrow space up to the internal parts, which is extremely advantageous. In this embodiment, it was shown that the sound insulation is mainly performed at a frequency of 1 KHz or more. However, since the frequency at which sound insulation is required differs depending on the vehicle, tuning is performed by changing the diameter of the hole or adjusting the gap according to these. It can be performed. Also, it goes without saying that not only two resonance systems but also three, four, and a plurality of systems can be produced.

7 and 8 show a third embodiment of the present invention.

FIG. 7 is a partially cutaway perspective view of the sound insulation wall 47 according to the third embodiment, and FIG. 8 is a sectional view of the same.

In this embodiment, a plurality of types, for example, two types of two-degree-of-freedom vibration systems 49 and 51 are provided. The vibration systems 49 and 51 are set so that the resonance frequencies are different. That is, the openings 53a and 53b of the vibration system 49 and the openings 55a and 55b of the vibration system 51 have different sizes. The openings 53a and 53b are smaller than the openings 55a and 55b, and the air mass m _a of the air 57 in the openings 53a and 53b is the air mass m _b of the air 59 in the openings 55a and 55b.
Is smaller than m _a <m _b . Also, the sound insulation plate 2
The partition wall 31 between the sound insulation plates 23 and 25 of the vibration system 51 is also closer to the vibration system 51 side than the volume of the air layer between the sound insulation plates 23 and 25 of the vibration system 51. The volume is large, and the spring constants of both vibration systems 49 and 51 are k _a <k _b . Therefore, the openings 53a, 53
Unlike the resonance frequency of b of air mass m _a and the vibration system 49 comprising a spring constant k _a of the air spring 37a, the resonance frequency of the vibration system 51 consisting of the air mass m _b and spring constant k _b of the air spring 37b is, Two types of vibration systems with two degrees of freedom will be created.

The resonance frequencies of these vibration systems 49 and 51 are

[Equation 2] It is represented by. For example, the frequency f ₂ is the resonance frequency of the vibration system 49, and the frequency f ₃ is the resonance frequency of the vibration system 51. The frequency of the sound for the purpose of sound insulation is the resonance frequency f with the frequency f ₂ minimized and the frequency f ₃ maximized.
The frequency band is set between ₂ and f ₃ . For example, the frequency band of engine noise is 1 to
Since the frequency is 2.5 kHz, the minimum frequency f ₂ is 1 kHz.
It is less than Hz and the maximum frequency f ₃ is set to exceed 2.5 kHz.

By doing so, the transmitted waves of the vibration system 49 and the vibration system 51 have opposite phases and cancel each other, so that a sound insulation effect can be obtained.

FIG. 9 shows the calculation result for confirming the effect of the third embodiment. In FIG. 9, β ₂ is the vibration system 4
The ratio of the volume of the air layer between the sound insulating plates 23 and 25 of both 9 and 51 is represented. That is, in FIG. 9, β ₂ is 0.2,0.
It changes like 3, 0.4, and 0.5. In each case, it was confirmed that the transmission loss increased in a certain frequency range and that it had a sound insulation effect.

Therefore, in this embodiment, the same effect as that of the second embodiment is obtained, and the sound insulation effect can be more surely provided by specifying the sound insulation region.

10 and 11 show a fourth embodiment.

FIG. 10 is a partially cutaway perspective view of the sound insulation wall 57, and FIG. 11 is a sectional view of the same. This embodiment is shown in FIG.
It is a modification of the second embodiment of FIG. That is, the two-degree-of-freedom vibration system 59 has openings 61 a and 61 b, and an intermediate plate 63 is provided between the sound insulating plates 23 and 25.
An intermediate opening portion 65 is provided in the first and second portions to form a triple structure.
The air mass m _c of the air 66 in the intermediate opening 65 is equal to the opening 61.
It is set smaller than the air mass m of a and 61b.
The air layers between the sound insulating plates 23 and 25 and the intermediate plate 63 respectively form the air springs 67 having the spring constant k _c . Therefore, the vibration system 59 in this embodiment constitutes a three-degree-of-freedom vibration system. The vibration system 45 connected by the tubular portion 41 constitutes a vibration system having one degree of freedom as described above. And the vibration system 59 with the three degrees of freedom is

[Equation 3] It has two resonance frequencies.

These two resonance frequencies f ₄ and f ₅ are f ₄
There is a relationship of <f ₅ and there is a relationship between the minimum resonance frequency and the next minimum resonance frequency. Then, it is set such that the frequency of the sound for the purpose of sound insulation is the frequency band between the resonance frequency f _4, f _5. For example, it is the frequency band 1~2.5kHz the engine noise is set to be between the frequency f ₄ and f _5. Therefore, when the engine noise is transmitted through the sound insulation wall 57, the transmitted waves have an opposite phase in the vibration system 59 and have a sound insulation effect.

FIG. 12 shows a calculation result confirming the effect of the fourth embodiment. In this embodiment, the sound insulation plates 23, 25,
The transmission loss of the sound insulation wall 57 was obtained by changing the ratio of the number of openings connected by the tubular portion 41 to all the openings of the intermediate plate 63. That is, it was confirmed that the transmission loss was increased in a specific frequency range, and that it had a sound insulation effect.

Therefore, in this embodiment as well, in addition to the same effects as the above, it is possible to set two frequencies at which such transmission loss increases, and a large sound insulation result is obtained in the frequency band between these two. Have. A large sound insulation effect can be obtained in a wider frequency band.

FIG. 13 shows a sectional view of the fifth embodiment.

This embodiment is a modification of the second embodiment.
That is, the predetermined opening 27 not connected by the tubular portion 41.
The extension portions 69 projecting to the opposite sides of the sound insulation plates 23 and 25 are provided on a and 27b. In this embodiment, the air mass m _{d is set} by the extension 69 of the predetermined openings 27a and 27b.
To increase the resonance frequency. Further, the distance H between the sound insulating plates 23 and 25 can be increased, and the spring constant k _d of the air spring 37 is reduced to further reduce the resonance frequency. Therefore, in this embodiment as well, it is possible to achieve the same operational effect as the above-mentioned embodiment and to further reduce the size.

FIG. 14 shows a sectional view of the sixth embodiment. This embodiment is a modification of the fifth embodiment, and the sound insulation plate 2
A sound absorbing material 71 is provided in the air layer between 3 and 25. Therefore, the sound absorbing material 71 can also have a sound absorbing effect. Further, since the sound absorbing material is not provided in the openings 27a, 27b, 29a, 29b, the air permeability is not impaired.

Therefore, in this embodiment as well, the same operational effect as the above-mentioned embodiment can be obtained, and the sound insulation performance can be further improved.

[0062]

As is apparent from the above, according to the first aspect of the invention, the vibration system constituted by the air mass in the opening provided in the sound insulation plate and the air spring in the air layer between the sound insulation plates is used to suppress the incident sound. By shifting the phases by 180 degrees to create transmitted sounds of opposite phases, and the transmitted sounds cancel each other, it is possible to provide a sound insulation effect. Therefore, there is no need to increase the height between the sound insulation plates, and the overall size can be reduced. Moreover, since it has an opening, it does not impair the air permeability. Therefore, when it is used as an undercover of an automobile, etc., it becomes an extremely advantageous sound insulating wall structure.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, a plurality of types of vibration systems can be constituted by partition walls provided between the sound insulating plates, and the phases of the respective transmitted waves can be shifted. It can be achieved with an extremely simple structure.

According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, resonance is performed so that the frequency for sound insulation exists in the frequency band between the minimum and maximum of the resonance frequency. Since the frequency is set, the structure is extremely advantageous when the frequency of the sound intended for sound insulation is in the constant frequency band.

According to the fourth aspect of the present invention, the vibration system composed of the air mass and the air spring shifts the phase of the transmitted wave with respect to the opening communicated with the tubular portion, so that the same sound insulation effect can be obtained. Moreover, the breathability can be further improved by the opening portion communicated with the tubular portion.

According to the invention of claim 5, in addition to the effect of the invention of claim 4, since the resonance frequency of the vibration system is made smaller than the main frequency of the sound for sound insulation, the sound for sound insulation is reduced. When the main frequency exceeds the resonance frequency, the phase becomes 18
It is possible to achieve a reliable sound insulation effect with a 0 degree shift.

According to the invention of claim 6, in addition to the effect of the invention of claim 4, the resonance frequency of the vibration system has a minimum frequency and a resonance frequency of the next lowest frequency so that the frequency of the sound for the purpose of sound insulation falls within this frequency band. Since it is set to, reliable sound insulation can be performed.

In the invention of claim 7, claims 1 to 6 are provided.
In addition to the effect of the invention of 1., the sound insulation wall structure can be applied to the undercover of the engine room of a car, and it can be comfortably placed between the car's minimum ground clearance and the parts in the engine room, and yet maintain breathability. Sound insulation can be performed while.

According to the eighth aspect of the invention, in addition to the effects of the first to seventh aspects of the invention, the air mass at the opening is provided by providing the opening with an extension projecting to the opposite side of the sound insulation plate. Can be increased, sound can be insulated from a lower frequency, and the size can be further reduced.

According to the invention of claim 9, in addition to the effects of the inventions of claims 1 to 8, sound can be absorbed by the sound absorbing material, and more reliable sound insulation and miniaturization can be achieved.

[Brief description of drawings]

1A and 1B are sectional views of a sound insulating wall, FIG. 1A being a sectional view of an embodiment, and FIG. 1B being a sectional view equivalent to FIG.

FIG. 2 is a schematic side view of an automobile to which an embodiment is applied.

FIG. 3 is a bottom view of the same.

FIG. 4 is a partially cutaway perspective view of a sound insulation wall according to a second embodiment.

FIG. 5 is a sectional view of the same.

FIG. 6 is a graph of experimental results confirming the effect.

FIG. 7 is a partially cutaway perspective view of a sound insulation wall according to a third embodiment.

FIG. 8 is a sectional view of the same.

FIG. 9 is a graph of experimental results confirming the effect.

FIG. 10 is a partially cutaway perspective view of a sound insulation wall according to a fourth embodiment.

FIG. 11 is a sectional view of the same.

FIG. 12 is a graph of experimental results confirming the effect.

FIG. 13 is a sectional view of a sound insulation wall according to a fifth embodiment.

FIG. 14 is a sectional view of a sound insulation wall according to a sixth embodiment.

FIG. 15 is a schematic side view of an automobile provided with an under cover.

FIG. 16 is a bottom view of the same.

FIG. 17 is a sectional view of an engine room to which a conventional example is applied.

FIG. 18 is a perspective view of a noise control member.

FIG. 19 is a partially cutaway perspective view of a sound insulation wall as a premise.

FIG. 20 is a sectional view of the same.

[Explanation of symbols]

3 engine room 5 undercover 21 sound insulation wall 23 sound insulation plate 25 sound insulation plate 27a opening 27b opening 29a opening 29b opening 31 partition wall 33a vibration system 33b vibration system 37a air spring 37b air spring 37 air spring 39 sound insulation wall 41 tube section Partition wall) 43 Air 45 Vibration system 47 Sound insulation wall 49 Vibration system 51 Vibration system 53a Opening 53b Opening 55a Opening 55b Opening 57 Sound insulating wall 59 Vibrational system 61a Opening 61b Opening 63 Intermediate plate 65 Intermediate opening 67 67 Air spring 69 extension 71 acoustic material k spring constant k ₁ a spring constant k ₂ a spring constant k _a spring constant k _b a spring constant k _c a spring constant k _d spring constant m air mass m _a air mass m _b air mass m _c air mass m _d air mass

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[Procedure amendment]

[Submission date] August 16, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound insulation wall structure capable of exhibiting a sound insulation effect while maintaining air permeability.

[0002]

2. Description of the Related Art Conventionally, as an automobile to which a sound insulation wall structure is applied, there is one shown in FIGS. 15 and 16, for example. This automobile 1 has an under cover 5 attached to the lower portion of an engine room 3. The under cover 5 has a function of improving the aerodynamic characteristics of the lower portion of the automobile 1 and a function of protecting the components in the engine room 3 from pebbles and the like that are flipped up, and suppressing noise emitted from the engine room 3 to the outside of the vehicle. It has a function as a sound insulation wall. The effect of the undercover 5 as a sound insulation wall increases as the area increases. However, as the area of the under cover 5 is increased, the lower portion of the engine room 3 is sealed, and the air temperature in the engine room 3 rises. As a result, the temperature inside the engine room 3 becomes high, which may lead to an unfavorable state in terms of component durability. As described above, when installing the undercover 5 in the engine room 3, not only the noise suppression aspect but also the thermal aspect must be considered.

Therefore, there is a conventional one as shown in FIGS. 17 and 18 (see Japanese Patent Application Laid-Open No. 60-85043). That is, in this conventional example, the noise control member 7 is provided in the lower opening of the engine room 3 of the automobile 1 instead of the under cover. This noise control member 7 has a large number of hollow pipe lines 9. The hollow conduits 9 are arranged such that the conduit length becomes shorter from the central portion of the noise control member 7 to the peripheral portion thereof. With this structure, the phase of the sound radiated from the engine room 3 is shifted according to the difference in the length of the hollow pipes 9, and the sound is shielded by canceling each other. Therefore, in this conventional example, the noise can be shielded by the noise control member 7, and the heat in the engine room 3 can be released to the outside through the hollow pipe line 9 to lower the air temperature in the engine room 3. be able to.

[0004]

However, the size of the undercover is a problem when it is actually mounted on an automobile as an undercover or the like. In other words, in the case of the undercover 5 in the engine room 3, the minimum ground clearance must be taken into consideration because it is installed between the engine room components such as the engine and the road surface. Actually, the space where the under cover 5 can be installed is the space from the minimum ground clearance to the parts in the engine room. Therefore, the undercover is restricted by its size, especially its thickness. As described above, the noise control member 7 of FIG. 18 has a configuration in which the transmitted sounds cancel each other due to the phase difference due to the difference in the path length of the sound, that is, the difference in the length of the hollow conduit 9, so that the sound insulation effect is achieved. In order to obtain it, it is necessary to make the path length difference of the hollow pipe 9 by half wavelength. For this reason, in order to provide a sound insulation effect to a frequency having a relatively long wavelength, which is a problem with the noise outside the vehicle, the path length difference of the hollow pipe line 9 must be made long. There is a problem that it becomes too thick to be used as an undercover.

The applicant of the present application has already applied for a sound insulation wall structure for solving such a problem as shown in FIGS. 19 and 20 (Japanese Patent Application No. 57196/1993). That is, the sound insulation wall 10 is provided with at least two sound insulation plates 11 and 13 that are opposed to each other with a space therebetween, and the sound insulation plates 11 and 13 are provided with openings 11a and 13a that are opposed to each other. The air 15 existing in the openings 11a and 13a is an air mass m, and the air existing between the sound insulation plates 11 and 13 is an air spring 17 having a spring constant k.
A vibration system with two degrees of freedom is constituted by 7 and 7.

In such a two-degree-of-freedom vibration system, the vibration transmissivity is less than 1 at the resonance frequency or higher and enters the vibration isolation region. By utilizing such a mechanism, the sound insulation effect can be obtained by the sound insulation wall structure as shown in FIG. Therefore, it is not necessary to take a long path length difference as in FIGS. 17 and 18, and it is possible to reduce the distance between the sound insulating plates 11 and 13 and obtain the thin sound insulating wall 10 advantageous as an undercover.

On the other hand, the resonance frequency of the vibration system including the air mass m and the air spring 17 must be made smaller in order to obtain the sound insulation effect from the low frequency by the above structure. For this purpose, the distance between the sound insulating plates 11 and 13 is increased to reduce the spring constant k of the air spring 17, or the thickness of the sound insulating plate 11 is increased to increase the openings 11a and 13.
It was necessary to increase the mass m of the air 15 existing in a and further reduce the aperture ratio. However, if the distance between the sound insulation plates 11 and 13 is increased or the thickness is increased, the sound insulation wall 1
There is a problem in that the thinness of 0 is limited, and the air permeability is sacrificed when the aperture ratio is reduced.

Therefore, an object of the present invention is to provide a sound insulation wall structure which is air permeable and which can be made thinner and smaller.

[0009]

In order to solve the above-mentioned problems, the invention of claim 1 is provided with at least two sound insulating plates facing each other with a gap, and penetrating each of the sound insulating plates.
A vibrating system having openings facing each other, the air mass of the openings and an air spring of an air layer between the sound insulation plates, and the vibrating system having a plurality of different resonance frequencies. Characterize.

A second aspect of the present invention is the sound insulation wall structure according to the first aspect, wherein the plurality of types of vibration systems are provided between the sound insulation plates and partition a predetermined vibration system from other vibration systems. It is characterized by being formed of a wall.

The invention of claim 3 is the invention of claim 1 or claim 2.
The sound insulation structure according to claim 1, wherein the plurality of types of resonance frequencies are set such that a main frequency of sound intended for sound insulation exists in a frequency band between the minimum and the maximum of the resonance frequencies. Is characterized by. The invention of claim 4 has at least two sound insulating plates facing each other with a space, and a plurality of openings provided to penetrate each of the sound insulating plates and facing each other. Among them, a vibration system including an air mass of a predetermined opening and an air spring of an air layer between the sound insulation plates is provided, and openings other than the openings constituting the vibration system are provided between the sound insulation plates facing each other. It is characterized in that they are communicated with each other by a tubular portion having an inner surface having substantially the same cross section as the opening.

The invention of claim 5 is the sound insulation structure according to claim 4, wherein the resonance frequency of a vibration system formed by the air mass of the opening and the air spring of the air layer between the sound insulation plates is used for sound insulation. It is characterized in that it is lower than the main frequency of the sound to be.

According to a sixth aspect of the present invention, in the sound insulation wall structure according to the fourth aspect, the vibration system has a plurality of resonance frequencies, and the resonance frequencies are the main frequencies of sounds intended for sound insulation. It is characterized in that the frequency band is set between the minimum frequency and the next smallest frequency.

The invention of claim 7 is the sound insulation wall structure according to any one of claims 1 to 6, wherein the sound insulation plate is an undercover of an engine room of an automobile.

The invention of claim 8 is the sound insulation wall structure according to any one of claims 1 to 7, wherein the opening is provided with an extension portion projecting to the opposite side of the sound insulation plate.

A ninth aspect of the present invention is the sound insulating wall structure according to the first to eighth aspects, wherein a sound absorbing material is provided between the sound insulating plates.

A tenth aspect of the present invention is the sound insulation structure according to the first or second aspect, wherein the plurality of types of resonance frequencies are such that the main frequency of sound for sound insulation is the minimum of the resonance frequencies. It is characterized in that it is set to exist in a frequency band between the next smaller one.

[0018]

According to the invention of claim 1 of the above-mentioned means, in the sound insulating plates having the openings and facing each other, the air in the openings serves as an air mass and the air layer between the sound insulating plates acts as an air spring. Therefore, a pair of air masses are connected via an air spring to form a two-degree-of-freedom vibration system. Here, when sound enters from one of the vibration systems, the incident wave is transmitted to the other through the vibration system. At this time, when the frequency of the incident wave exceeds the resonance frequency of the vibration system, the phase of the transmitted wave is inverted by 180 degrees. Therefore, when a plurality of types having different resonance frequencies are provided as the vibration system, the phase of the transmitted wave from each different vibration system is 18
It is possible to create frequencies that are offset by 0 degrees, which causes the transmitted waves to cancel each other. Further, it is possible to ventilate the sound insulating plate from one side to the other side through the opening.

According to the invention of claim 2, in addition to the function of the invention of claim 1, a vibration system having different resonance frequencies can be formed by partition walls provided between the sound insulating plates.

In the invention of claim 3, in addition to the operation of the invention of claim 1 or claim 2, when the frequency of the sound for sound insulation exceeds the minimum resonance frequency, the phase of the transmitted wave is inverted by 180 degrees. Therefore, the phases of the transmitted waves in the vibration system having the maximum and minimum resonance frequencies are shifted by 180 degrees, and the sounds can be canceled by the transmitted waves.

According to the fourth aspect of the present invention, the portion in which the opening is communicated with the cylindrical portion having the inner surface of substantially the same cross section constitutes a one-degree-of-freedom vibration system having no resonance point. Therefore, there is no phase shift between the transmitted wave that has passed through this portion and the incident wave. On the other hand, the transmitted waves that have passed through the vibration system composed of the air mass and the air spring are out of phase. Therefore, both transmitted waves can cancel each other.

According to the invention of claim 5, in addition to the operation of the invention of claim 4, since the resonance frequency of the vibration system composed of the air mass and the air spring is smaller than the frequency of the sound for sound insulation,
The incident wave can be transmitted with a phase shift of 180 degrees.

According to the invention of claim 6, in addition to the operation of the invention of claim 4, the frequency of the sound for sound insulation is a frequency band between the minimum resonance frequency of the vibration system and the next minimum frequency. Therefore, the transmitted waves that have passed the minimum resonance frequency are 180 degrees out of phase with each other, and can cancel each other with the transmitted waves that have passed the other portions.

According to the invention of claim 7, the sound insulation wall structure can be used as an undercover of an engine room of an automobile.

According to the eighth aspect of the present invention, since the extension is provided in the opening so as to project toward the opposite side of the sound insulation plate, the mass of air in the opening can be increased and the resonance frequency can be reduced.

In the ninth aspect of the invention, sound can be absorbed by the sound absorbing material provided between the sound insulating plates.

According to the invention of claim 10, in addition to the effect of the invention of claim 1 or claim 2, the frequency for sound insulation exists in the frequency band between the minimum resonance frequency and the next smallest resonance frequency. Since the resonance frequency is set so that the transmitted waves that have passed the minimum resonant frequency are 180 degrees out of phase with each other, they can cancel each other with the transmitted waves that have passed the other portions.

[0028]

Embodiments of the present invention will be described below.

FIG. 1A is a schematic sectional view of a sound insulation wall 21 to which the sound insulation wall structure according to the first embodiment of the present invention is applied. The sound insulation wall 21 has two sound insulation plates 23 and 25 facing each other with a space. The sound insulation plates 23, 25
Need only have at least two, and the number can be further increased.

A plurality of openings 27a, 27b, 29a, 29b facing each other are provided through the sound insulation plates 23, 25, respectively. The sound insulation plate 2
A partition wall 31 is provided between 3 and 25. Therefore, a plurality of vibration systems 33a and 33b are provided, and the partition wall 3
1 has a configuration in which a predetermined vibration system 33a is partitioned from another vibration system 33b.

The vibration system 33a has openings 27a and 27b.
Sound insulation plate 2 surrounded by the mass m of the air 35 and the partition wall 31
It is composed of an air spring 37a composed of an air layer between 3, 25. The other vibration system 33b similarly has openings 29a,
It is composed of an air mass m of the air 35 of 29b and an air spring 37b. The difference of the air layer volume between compartmented noise insulating plates 23 and 25 with the spring constant k ₁ and the partition wall 31 and the spring constant k ₂ of the air spring 37b of the pneumatic spring 37a, k ₁ <k
There is a relationship of ₂ . Therefore, a plurality of types of vibration systems 33a and 33b having different resonance frequencies are provided. The plural kinds of resonance frequencies of the vibration systems 33a and 33b are set so that the frequency of the sound for sound insulation exists in the frequency band between the minimum and the maximum of the resonance frequency.

The setting of the plural kinds of resonance frequencies will be described in comparison with the vibration system shown in the prior application of FIG. 1 (b).

In FIG. 1B, partition walls 31 between the sound insulating plates 11 and 13 are evenly provided for the openings 11a and 13b. When the partition plates 31 are evenly provided in this way, it is equivalent to the sound insulation wall 10 described with reference to FIGS.
That is, the sound insulation wall 10 described with reference to FIGS. 19 and 20 does not have a partition wall, but the spring constants of the air springs 17 with respect to the air mass m of each air 15 are all equal, and as shown in FIG. It is equivalent to a case in which all the air layer volumes are divided. Therefore, as shown in FIG.
When the size of the air layer divided by 1 is different, an increase in the volume of the air layer corresponds to a decrease in the spring constant of the air spring, and the resonance frequency of the predetermined vibration system 33a is different from that of other vibrations. It becomes smaller than the resonance frequency of the system 33b.

When sound enters from one of the sound insulation walls 21, the incident wave is transmitted to the other through the vibration systems 33a and 33b. At this time, when the frequency of the incident wave exceeds the resonance frequency of the vibration system, the phase of the transmitted wave is inverted by 180 degrees. Therefore, in this embodiment in which the vibration systems 33a and 33b having large and small resonance frequencies are provided, the phase of the transmitted wave is shifted by 180 degrees when the resonance frequency of the smaller vibration system 33a is exceeded. Further, since the resonance system is formed so that the frequency of the sound intended for sound insulation exists in the frequency band between the large and small resonance frequencies, the transmitted wave of the vibration system 33b having a large resonance frequency has no phase shift. . Therefore, the noises transmitted through both the vibration systems 33a and 33b cancel each other out, and a sound insulation effect can be provided in this frequency band. Further, regarding ventilation, one of the openings 27a, 27b, 2 from the sound insulation wall 21
Air can pass through 9a and 29b to provide sufficient air permeability.

In addition, in this embodiment, FIG.
As is clear from comparison with (b), the device can be downsized. That is, FIG. 1B shows the partition wall 3
1, but the partition wall 31 has the entire opening 11a,
It is equidistant from 11b, which is equivalent to the case where no partition wall exists between the sound insulation plates 11 and 13 in FIGS. In contrast to FIG. 1 (b), in the case of FIG. 1 (a), the partition wall 31 is moved closer to the openings 29a and 29b, so that the partition wall 31 has an opening when compared with FIG. 1 (b). It is in a state of moving away from the portions 27a and 27b. Therefore, the air mass of the air layer between the sound insulating plates 23 and 25 in the openings 27a and 27b becomes relatively large, and the spring constant of the air spring 37a can be reduced.
Therefore, the resonance frequency of the vibration system 33a becomes small. This means that when the same size as that of FIG. 1 (b) is considered, the sound insulation effect is obtained from a lower frequency, and conversely, when the sound insulation effect is provided from the same frequency, Since it is not necessary to increase the thickness to secure the volume of the air chamber and reduce the spring constant k, the one shown in FIG. 1 (a) can be made smaller than that shown in FIG. 1 (b). It becomes.

Next, another embodiment will be described. In the following embodiments, the same components as those in the above embodiment will be denoted by the same reference numerals and will not be described.

2 and 3 show a second embodiment.

In this embodiment, a sound insulation wall structure is applied to the under cover 5 of the automobile 1. That is, the under cover 5 is provided in the lower part of the engine room 3, and the sound insulation wall 39 is integrally provided on the rear side thereof. The concrete construction of the sound insulation wall 39 of the second embodiment is as shown in FIGS.

In this embodiment, each of the plurality of openings 27a,
Predetermined openings 27a, 2 of 27b, 29a, 29b
The air mass m of the air 35 of 7b and the air spring 37 having the spring constant k of the air layer between the sound insulating plates 23 and 25 constitute a vibration system 33a having two degrees of freedom. Further, the openings 29a and 29b other than the openings 27a and 27b constituting the vibration system 33a are communicated with each other by the tubular portion 41. The tubular portion 41 is provided between the sound insulating plates 23 and 25 that face each other, and has an inner surface having substantially the same cross section as the openings 29a and 29b. Therefore, the openings 29a, 2
The vibration system configured by 9b and the cylindrical portion 41 has an opening 29
The entire air 43 from a, 29b to the tubular portion 41 acts as an air mass M, and constitutes a vibration system 45 with one degree of freedom. This one-degree-of-freedom vibration system 45 does not have a resonance point, and the incident wave and the transmitted wave always have the same phase. On the other hand, the vibration system 33a having two degrees of freedom has a resonance frequency represented by the following equation.

[0040]

[Equation 1] The resonance frequency of the two-degree-of-freedom vibration system 33 is set to be lower than the frequency of sound intended for sound insulation. That is, in the case of engine noise of automobile 1, its frequency band is 1
.About.2.5 kHz, and the resonance frequency shown by the equation (1) is set to less than 1 kHz.

Therefore, in this embodiment, the engine room 3
When noise that leaks from the outside into the undercover 5 is incident on the undercover 5, the incident wave passes through as a transmitted wave having the same phase in the vibration system 45 with one degree of freedom, and the vibration system 3 with two degrees of freedom is used.
In 3a, the phase is shifted by 180 degrees and the light is transmitted by exceeding the resonance frequency represented by the equation (1). Therefore, the transmitted waves that have passed through the vibration system 45 and the vibration system 33a have mutually opposite phases and cancel each other, so that a sound insulation effect can be obtained. Especially in the case of engine noise of the automobile 1,
Since the frequency band is 1 to 2.5 kHz, the sound insulation wall 39 of the under cover 5 can have a reliable sound insulation effect against engine noise by setting the resonance frequency of the above formula (1) to less than 1 kHz. Of.

FIG. 6 is a calculation result confirming the effect of the sound insulation wall 39. In FIG. 6, β ₁ indicates the ratio of the number of openings 29a, 29b connected by the tubular portion 41 to the total number of openings 27a, 27b, 29a, 29b on the sound insulation wall 39. Then, the transmission loss of the sound insulation wall 39 was obtained by changing the ratio from 0 to 1. According to this, β
It was confirmed that when ₁ = 0.25, β ₁ = 0.5, β ₁ = 0.75, etc., the transmission loss was large and a sound insulation effect was obtained.

Further, in comparison with FIG. 1A, the tubular portion 41 has
Further, since the openings 29a and 29b are close to each other, it is possible to further reduce the size.

Further, in the second embodiment as well, the openings 27a,
Air permeability can be secured due to 29a, 27b, 29b, and hot air in the engine room 3 can be easily released to the outside.

Therefore, the under cover 5 of the automobile 1 is breathable and the engine room 3 from the minimum ground clearance.
It can be installed in a narrow space up to the internal parts, which is extremely advantageous. In this embodiment, it was shown that the sound insulation is mainly performed at a frequency of 1 KHz or more. However, since the frequency at which the sound insulation is required differs depending on the vehicle, the tuning is performed by changing the diameter of the hole or adjusting the gap accordingly. It can be performed. Also, it goes without saying that not only two resonance systems but also three, four, and a plurality of systems can be produced.

7 and 8 show a third embodiment of the present invention.

FIG. 7 is a partially cutaway perspective view of the sound insulation wall 47 according to the third embodiment, and FIG. 8 is a sectional view of the same.

In this embodiment, a plurality of types, for example, two types of two-degree-of-freedom vibration systems 49 and 51 are provided. The vibration systems 49 and 51 are set so that the resonance frequencies are different. That is, the openings 53a and 53b of the vibration system 49 and the openings 55a and 55b of the vibration system 51 have different sizes. The openings 53a and 53b are smaller than the openings 55a and 55b, and the air mass m _a of the air 57 in the openings 53a and 53b is the air mass m _b of the air 59 in the openings 55a and 55b.
Is smaller than m _a <m _b . Also, the sound insulation plate 2
The partition wall 31 between the sound insulation plates 23 and 25 of the vibration system 51 is also closer to the vibration system 51 side than the volume of the air layer between the sound insulation plates 23 and 25 of the vibration system 51. The volume is large, and the spring constants of both vibration systems 49 and 51 are k _a <k _b . Therefore, the openings 53a, 53
Unlike the resonance frequency of b of air mass m _a and the vibration system 49 comprising a spring constant k _a of the air spring 37a, the resonance frequency of the vibration system 51 consisting of the air mass m _b and spring constant k _b of the air spring 37b is, Two types of vibration systems with two degrees of freedom will be created.

The resonance frequencies of these vibration systems 49 and 51 are

[Equation 2] It is represented by. For example, the frequency f ₂ is the resonance frequency of the vibration system 49, and the frequency f ₃ is the resonance frequency of the vibration system 51. The frequency of the sound for the purpose of sound insulation is the resonance frequency f with the frequency f ₂ minimized and the frequency f ₃ maximized.
The frequency band is set between ₂ and f ₃ . For example, the frequency band of engine noise is 1 to
Since the frequency is 2.5 kHz, the minimum frequency f ₂ is 1 kHz.
It is less than Hz and the maximum frequency f ₃ is set to exceed 2.5 kHz.

By doing so, the transmitted waves of the vibration system 49 and the vibration system 51 have opposite phases and cancel each other, so that a sound insulation effect can be obtained.

FIG. 9 shows the calculation result for confirming the effect of the third embodiment. In FIG. 9, β ₂ is the vibration system 4
The ratio of the volume of the air layer between the sound insulating plates 23 and 25 of both 9 and 51 is represented. That is, in FIG. 9, β ₂ is 0.2,0.
It changes like 3, 0.4, and 0.5. In each case, it was confirmed that the transmission loss increased in a certain frequency range and that it had a sound insulation effect.

Therefore, in this embodiment, the same effect as that of the second embodiment is obtained, and the sound insulation effect can be more surely provided by specifying the sound insulation region.

10 and 11 show a fourth embodiment.

FIG. 10 is a partially cutaway perspective view of the sound insulation wall 57, and FIG. 11 is a sectional view of the same. This embodiment is shown in FIG.
It is a modification of the second embodiment of FIG. That is, the three-degree-of-freedom vibration system 59 has openings 61a and 61b, and an intermediate plate 63 is provided between the sound insulating plates 23 and 25.
An intermediate opening portion 65 is provided in the first and second portions to form a triple structure.
The air mass m _c of the air 66 in the intermediate opening 65 is equal to the opening 61.
It is set smaller than the air mass m of a and 61b.
The air layers between the sound insulating plates 23 and 25 and the intermediate plate 63 respectively form the air springs 67 having the spring constant k _c . Therefore, the vibration system 59 in this embodiment constitutes a three-degree-of-freedom vibration system. The vibration system 45 connected by the tubular portion 41 constitutes a vibration system having one degree of freedom as described above. And the vibration system 59 with the three degrees of freedom is

[Equation 3] It has two resonance frequencies.

These two resonance frequencies f ₄ and f ₅ are f ₄
There is a relationship of <f ₅ and there is a relationship between the minimum resonance frequency and the next minimum resonance frequency. Then, it is set such that the frequency of the sound for the purpose of sound insulation is the frequency band between the resonance frequency f _4, f _5. For example, it is the frequency band 1~2.5kHz the engine noise is set to be between the frequency f ₄ and f _5. Therefore, when the engine noise is transmitted through the sound insulation wall 57, the transmitted waves have an opposite phase in the vibration system 59 and have a sound insulation effect.

FIG. 12 shows a calculation result confirming the effect of the fourth embodiment. In this embodiment, the sound insulation plates 23, 25,
The transmission loss of the sound insulation wall 57 was obtained by changing the ratio of the number of openings connected by the tubular portion 41 to all the openings of the intermediate plate 63. That is, it was confirmed that the transmission loss was increased in a specific frequency range, and that it had a sound insulation effect.

Therefore, in this embodiment as well, in addition to the same effects as the above, it is possible to set two frequencies at which such transmission loss increases, and a large sound insulation result is obtained in the frequency band between these two. Have. A large sound insulation effect can be obtained in a wider frequency band. FIG. 13 shows a sectional view of the fifth embodiment.

This embodiment is a modification of the second embodiment.
That is, the predetermined opening 27 not connected by the tubular portion 41.
The extension portions 69 projecting to the opposite sides of the sound insulation plates 23 and 25 are provided on a and 27b. In this embodiment, the air mass m _{d is set} by the extension 69 of the predetermined openings 27a and 27b.
To increase the resonance frequency. Further, the distance H between the sound insulating plates 23 and 25 can be increased, and the spring constant k _d of the air spring 37 is reduced to further reduce the resonance frequency. Therefore, in this embodiment as well, it is possible to achieve the same operational effect as the above-mentioned embodiment and to further reduce the size.

FIG. 14 shows a sectional view of the sixth embodiment. This embodiment is a modification of the fifth embodiment, and the sound insulation plate 2
A sound absorbing material 71 is provided in the air layer between 3 and 25. Therefore, the sound absorbing material 71 can also have a sound absorbing effect. Further, since the sound absorbing material is not provided in the openings 27a, 27b, 29a, 29b, the air permeability is not impaired.

Therefore, in this embodiment as well, the same effect as the above embodiment can be obtained, and the sound insulation performance can be further improved.

[0061]

As is apparent from the above, according to the first aspect of the invention, the vibration system constituted by the air mass in the opening provided in the sound insulation plate and the air spring in the air layer between the sound insulation plates is used to suppress the incident sound. By shifting the phases by 180 degrees to create transmitted sounds of opposite phases, and the transmitted sounds cancel each other, it is possible to provide a sound insulation effect. Therefore, there is no need to increase the height between the sound insulation plates, and the overall size can be reduced. Moreover, since it has an opening, it does not impair the air permeability. Therefore, when it is used as an undercover of an automobile, etc., it becomes an extremely advantageous sound insulating wall structure.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, a plurality of types of vibration systems can be constituted by partition walls provided between the sound insulating plates, and the phases of the respective transmitted waves can be shifted. It can be achieved with an extremely simple structure.

According to the invention of claim 3, in addition to the effect of the invention of claim 1 or claim 2, resonance is performed so that the frequency for sound insulation exists in the frequency band between the minimum and maximum of the resonance frequency. Since the frequency is set, the structure is extremely advantageous when the frequency of the sound intended for sound insulation is in the constant frequency band.

According to the fourth aspect of the present invention, the vibration system composed of the air mass and the air spring shifts the phase of the transmitted wave with respect to the opening communicated with the cylindrical portion, so that the same sound insulation effect can be obtained. Moreover, the breathability can be further improved by the opening portion communicated with the tubular portion.

According to the invention of claim 5, in addition to the effect of the invention of claim 4, since the resonance frequency of the vibration system is made smaller than the main frequency of the sound for sound insulation, the sound for sound insulation is reduced. When the main frequency exceeds the resonance frequency, the phase becomes 18
It is possible to achieve a reliable sound insulation effect with a 0 degree shift.

According to the invention of claim 6, in addition to the effect of the invention of claim 4, the resonance frequency of the vibration system has a minimum value and a resonance frequency which is the next smallest, so that the frequency of the sound for the purpose of sound insulation falls within this frequency band. Since it is set to, reliable sound insulation can be performed.

In the invention of claim 7, claims 1 to 6 are provided.
In addition to the effect of the invention of 1., the sound insulation wall structure can be applied to the undercover of the engine room of a car, and it can be comfortably placed between the car's minimum ground clearance and the parts in the engine room, and yet maintain breathability. Sound insulation can be performed while.

According to the invention of claim 8, in addition to the effects of the inventions of claims 1 to 7, the air mass at the opening is provided by providing the opening with an extension projecting to the opposite side of the sound insulating plate. Can be increased, sound can be insulated from a lower frequency, and the size can be further reduced.

According to the invention of claim 9, in addition to the effects of the inventions of claims 1-8, sound can be absorbed by the sound absorbing material, and more reliable sound insulation and miniaturization can be achieved.

According to the invention of claim 10, in addition to the effect of the invention of claim 1 or 2, the resonance frequency of the vibration system has a minimum and a resonance frequency of the second smallest, and the purpose is to isolate sound in this frequency band. Since the frequency of the sound to be heard is set, the sound can be surely insulated.

[Procedure amendment]

[Submission date] October 12, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction content]

[0040]

[Equation 1] The resonance frequency of the two-degree-of-freedom vibration system 33 is set to be lower than the frequency of sound intended for sound insulation. That is, in the case of engine noise of automobile 1, its frequency band is 1
.About.2.5 kHz, and the resonance frequency shown by the equation (1) is set to less than 1 kHz.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction content]

The resonance frequencies of these vibration systems 49 and 51 are

[Equation 2] It is represented by. For example, the frequency f ₂ is the resonance frequency of the vibration system 49, and the frequency f ₃ is the resonance frequency of the vibration system 51. The frequency of the sound for the purpose of sound insulation is the resonance frequency f with the frequency f ₂ minimized and the frequency f ₃ maximized.
The frequency band is set between ₂ and f ₃ . For example, the frequency band of engine noise is 1 to
Since the frequency is 2.5 kHz, the minimum frequency f ₂ is 1 kHz.
It is less than Hz and the maximum frequency f ₃ is set to exceed 2.5 kHz.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0054

[Correction method] Change

[Correction content]

FIG. 10 is a partially cutaway perspective view of the sound insulation wall 57, and FIG. 11 is a sectional view of the same. This embodiment is shown in FIG.
It is a modification of the second embodiment of FIG. That is, the three-degree-of-freedom vibration system 59 has openings 61a and 61b, and an intermediate plate 63 is provided between the sound insulating plates 23 and 25.
An intermediate opening portion 65 is provided in the first and second portions to form a triple structure.
The air mass m _c of the air 66 in the intermediate opening 65 is equal to the opening 61.
It is set smaller than the air mass m of a and 61b.
The air layers between the sound insulating plates 23 and 25 and the intermediate plate 63 respectively form the air springs 67 having the spring constant k _c . Therefore, the vibration system 59 in this embodiment constitutes a three-degree-of-freedom vibration system. The vibration system 45 connected by the tubular portion 41 constitutes a vibration system having one degree of freedom as described above. And the vibration system 59 with the three degrees of freedom is

[Equation 3] It has two resonance frequencies.

Claims (9)

[Claims] 1. At least two sound insulating plates facing each other with a space, and openings provided so as to penetrate through each of the sound insulating plates and facing each other, the air mass of the opening and the sound insulating plate. A sound insulation wall structure comprising: a vibration system including an air spring in an air layer between the vibration systems, wherein the vibration system is provided in a plurality of types having different resonance frequencies. 2. The sound insulation wall structure according to claim 1, wherein the plurality of types of vibration systems are formed by partition walls that are provided between the sound insulation plates and partition a predetermined vibration system from other vibration systems. Sound insulation wall structure featuring. 3. The sound insulation structure according to claim 1, wherein the plurality of types of resonance frequencies have a main frequency of sound for sound insulation between a minimum and a maximum of the resonance frequencies. A sound insulation wall structure characterized by being set to exist in a frequency band. 4. At least two sound insulating plates facing each other with a space, and a plurality of openings provided so as to penetrate each of the sound insulating plates and facing each other. A vibration system including an air mass of a predetermined opening and an air spring of an air layer between the sound insulation plates, and the openings other than the openings constituting the vibration system are provided between the sound insulation plates facing each other. A sound-insulating wall structure, characterized in that it is communicated with a tubular portion having an inner surface of substantially the same cross-section as the portion. 5. The sound insulation wall structure according to claim 4, wherein a resonance frequency of a vibration system including an air mass of the opening and an air spring of an air layer between the sound insulation plates is determined by a main sound of a sound intended for sound insulation. Sound insulation wall structure characterized by being smaller than the frequency. 6. The sound insulation structure according to claim 4, wherein a plurality of types of the vibration system are provided so as to have different resonance frequencies, and the resonance frequency is a main frequency of a sound intended for sound insulation. A sound insulation wall structure characterized by being set to have a frequency band between the smallest and the next smallest. 7. The sound-insulating wall structure according to claim 1, or claim 2, or claim 3, or claim 4, or claim 5, or claim 6, wherein the sound-insulating plate is an engine room of an automobile. The sound insulation wall structure, which is a part or the whole of the undercover of. 8. The sound insulation wall structure according to claim 1, or 2, or 3, or 4, or 5, or 6, or 7, wherein: , A sound insulation wall structure characterized in that an extension portion is provided projecting to the opposite side of the sound insulation plate. 9. The method according to claim 1, claim 2, or claim 3,
The sound insulation wall structure according to claim 4, or claim 5, or claim 6, or claim 7, or claim 8, wherein a sound absorbing material is provided in an air layer between the sound insulating plates. Sound insulation wall structure.